The present Invention relates, in general, to a novel device for modulating the amplitude and phase of millimeter wavelength signals and, more particularly, to a novel device for modulating the amplitude and phase of millimeter wavelength signals in a fin-line waveguide configuration.
Recently there has been a dramatic interest in the development of millimeter wavelength components and, in particular, in non-reciprocal components. Fabrication cost, propagation losses, and device efficiency are all important criteria to be considered at millimeter wavelengths. Presently the fin-line waveguide configuration is believed to offer the best opportunity in meeting all of the above criteria.
The fin-line waveguide configuration is a relatively new type of waveguide transmission line which, in addition to the above mentioned criteria, offers distinct advantages in power handling capacity and bandwidth as compared to conventional waveguides. In its most basic form, the fin-line comprises a rectangular waveguide loaded with a slab of dielectric material positioned across the center of the waveguide in the plane of the electric field. The dielectric slab has the effect of adding capacitance to the dominant mode of resonance while only slightly changing the capacitance associated with adjacent modes. Thus the dielectric slab effectively increases the separation between the first two modes of propogation thereby providing a wider useful bandwidth than conventional waveguides. Additionally, because the dielectric slab has an inherently high breakdown strength relative to air, the slab adds a material having high breakdown strength to the waveguide in a region where breakdown is more likely to occur. As a result, the power handling capability is increased in the fin-line waveguide as compared to conventional waveguides. A thorough description of fin-line waveguides appears in P. J. Meier, "Integrated Fin-Line Millimeter Components," IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-22, No. 12, December 1974, pages 1209-1216. The contents of this article are incorporated herein by reference.
The present Invention provides a novel means for modulating the phase and amplitude of millimeter wavelength signals passing through a fin-line waveguide.